This invention is concerned with an adhesive-applying machine for applying adhesive progressively to selected portions of a workpiece surface, e.g. marginal portions of a lasted shoe bottom or of the attachment surface of a shoe sole, said machine comprising a work support for supporting a workpiece to selected portions of a surface of which adhesive is to be applied, a mounting for an adhesive applicator, and first motor means operable under programmed control for effecting relative movement between the work support and mounting, and thus between an applicator supported by the mounting and the surface of a workpiece supported by the work support, in directions extending lengthwise and widthwise of the workpiece surface whereby such applicator is caused to follow a desired path relative to the workpiece surface, and also in a direction extending heightwise of the workpiece surface thus to follow the heightwise contour thereof.
One such machine is described in U.S. Pat. No. 4,951,338, being a machine for applying adhesive progressively along marginal portions of lasted shoe bottoms (although, it will be appreciated, such a machine could readily also be used for applying adhesive to the attachment surface of a shoe sole, with the necessary modification to the work support). In this machine the adhesive applicator comprises a nozzle the outlet of which is surrounded by a brush element which is rotatable whereby to spread adhesive supplied through said nozzle over the surface of the marginal portion of the shoe bottom. Using such an applicator, it has been found that a relatively uniform coating of adhesive can be applied to the shoe bottom, and moreover the band of adhesive thus applied has a relatively clearly defined edge, which is of course necessary when applying adhesive for sole attaching, since if the adhesive extends in the finished shoe beyond the edge of the attached sole the finished shoe has an unsightly appearance, whereas if the adhesive band does not extend up to the outsole edge a risk of insecure attachment of the sole arises.
The quantity of adhesive applied progressively to a workpiece surface depends upon the rate of supply of adhesive to the applicator and also the speed at which the applicator traverses the workpiece surface. Whereas for most shoes the rotary brush system referred to above has been found to be adequate in terms of both the thickness of the applied adhesive and also the operational speed (machine cycle time), in some circumstances it has been found that in order to achieve the desired thickness of the applied layer the speed of traverse of the applicator has to be reduced to a speed which is unacceptable in terms of shoe factory output. Similarly, in some cases it has been desirable to operate the machine at a higher operational speed than is normally set, and again this increase in operational speed can be achieved only with a commensurate detrimental effect on the applied layer.
In addition, in the case of shoes with seams, it has sometimes been found that, because of the characteristics of adhesive flow using the rotary brush system, dry spots may occur immediately "downstream" of a seam, again with detrimental effects in terms of the secureness of the adhesive bond.